Biological synergy of greener gold nanoparticles by using Coleus aromaticus leaf extract.

Greener nanotechnology plays an important role in developing alternative and effective treatment strategies for various diseases. Biological synthesis of metal nanoparticles (MNPs) has known to possess suitable alternatives than the existing chemical methods. Greener synthesis of MNPs by using plant extracts has become an emerging field due to their safe, eco-friendly and non-toxic nature that are suitable for synergistic biological activities. Hence, the greener method is chosen by the present study. In the present study, the greener synthesis of gold nanoparticles (AuNPs) was successfully done by using Coleus aromaticus leaf extract at three different temperatures (30 °C, 60 °C and 100 °C). The formation of AuNPs was initially monitored by visual observation and then characterized with the help of diverse techniques like UV-Vis spectroscopy (UV-Vis), X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, Scanning Electron Microscopy (SEM), High Resolution-Transmission Electron Microscopy (HR-TEM) and dynamic light scattering (DLS). Surface plasmon resonance (SPR) peak and crystalline nature of AuNPs were obtained by UV-Vis and XRD spectroscopies respectively. FT-IR analysis shows the different characteristic functional groups in turn responsible for the bio-reduction of gold ions by using leaf extract. The formations of different nano-sized AuNPs with their different morphologies were observed by SEM and HR-TEM analyses. Surface charge and stability of the AuNPs were measured by zeta potential and DLS respectively. The synthesized AuNPs coated with cotton fabric was analyzed by UV-Diffuse Reflectance Spectroscopy (UV-DRS), which revealed excellent UV protection against UV radiation. The AuNPs coated cotton fabric exhibited remarkable antibacterial sensitivity against Staphylococcus epidermidis and Escherichia coli. Further, the synthesized AuNPs showed significant cytotoxicity against human liver cancer (HepG2) cell line. The findings of this study revealed that, AuNPs synthesized using Coleus aromaticus leaf extract could be an alternative, safe, and effective source of UV protection, antibacterial and anticancer agents.

Improved conductivity and antibacterial activity of poly(2-aminothiophenol)-silver nanocomposite against human pathogens.

A rapid and simple chemical synthesis of poly(2-aminothiophenol)­silver (P2ATP-Ag) nanocomposite using conductive and electroactive silver nanoparticles (AgNPs) is reported. The AgNPs was synthesized by chemical reduction method using tri­sodium citrate as reducing agent and poly(N-vinyl-2-pyrrolidone) (PVP) as stabilizing agent. P2ATP-Ag nanocomposite was synthesized by using potassium peroxodisulphate as oxidant and the samples were characterized. The presence of AgNPs in the composite was confirmed from UV-Vis, FTIR and X-ray diffraction studies. Morphology of the P2ATP and its composite were investigated by SEM. HR-TEM images show spherical, trigonal and rod like morphologies with sizes of Ag nanoparticles and its composite. Thermal analysis revealed that the thermal stability of the P2ATP-Ag nanocomposite is improved when compared with pure P2ATP. The synthesized AgNPs, pure P2ATP and P2ATP-Ag nanocomposite were screened for antibacterial activity test against human pathogen such as Gram positive (Bacillus subtilis, ATCC-6051) and Gram negative (Vibrio cholerae, ATCC-14035), carried out by agar-well diffusion method at micro molar concentration. The result shows that P2ATP-Ag nanocomposite has excellent antibacterial activity due to the presence of Ag nanoparticles. The electrical conductivity of the P2ATP-Ag nanocomposite is better than that of pure P2ATP. The reported nanocomposite will be a potential material for electrocatalysis, sensors and biomedical applications.

Voltammetric determination of nitroaromatic and nitramine explosives contamination in soil.

The contamination of soil by nitroaromatic and nitramine explosives is widespread during the manufacture, testing and disposal of explosives and ammunitions. The analysis for the presence of trace explosive contaminants in soil becomes important in the light of their effect on the growth of different varieties of plants and crops. 2,4,6-Trinitrotoluene (TNT), cyclotrimethylene trinitramine (Research Department explosive, RDX) and cyclotetramethylene tetranitramine (high melting point explosive, HMX), other related explosive compounds and their by-products must be monitored in soil and surrounding waterways since these are mutagenic, toxic and persistent pollutants that can leach from the contaminated soil to accumulate in the food chain. In this study, a voltammetric method has been developed for the determination of explosive such as RDX, HMX and TNT. The electrochemical redox behavior of RDX, HMX and TNT was studied through cyclic voltammetry and quantitative determination was carried out by using square wave voltammetry technique. Calibration curves were drawn and were linear in the range of 63-129ppm for RDX with a detection limit of 10ppm, 49-182ppm for HMX with a detection limit of 1ppm and 38-139ppm for TNT with a detection limit of 1ppm. This method was applied to determine the contaminations in several soil samples that yielded a relative error of 1% in the concentrations.